This invention relates to hygrometers and more particularly to a hydrometer that will measure relative humidity just below and just above 100%.
Heretofore relative humidity (RH) devices have been able to make measurements in the range from 0 to about 95%; however, the prior art instruments rapidly loose their accuracy for RH values greater than 95% and some are destroyed at an RH of 100% due to their interaction with the water vapor. Such instruments include a dry substance-type in which the gain in weight due to water vapor is a measure of the relative humidity. Another type consists of a brightly polished surface which is cooled until vapor from the air begins to form on the surface and the temperature at which the vapor forms is a determining factor as to the relative humidity. Another type is the wet bulb-type. A further type includes a pointer connected to a slender axle about which a suitable material is wrapped which rotates the axle in either direction as the water vapor content in the air varies.